Tube with external longitudinal ribs



y 1958 K. E. SCHOLTEN 2,835,275

- TUBE WITH EXTERNAL LONGITUDINAL RIBS Filed Sept. 4, 1953 [fit 8175071 2,835,275 Patented May 20, 1958 TUBE WITH EXTERNAL LONGITUDINAL RIBS Karl Ernst Scholten, Witten (Ruhr), Germany, assignor to Mannesmann Alrtiengesellschaft, Dusseldorf, Ger many, a German company Application September 4, 1953, Serial No, 378,498

' 1 Claim. (c1. 138-70 The present invention relates to the formation of a seamless tube with external longitudinal ribs as known per se and consists in that the said external ribs are produced by cold pilger-step rolling.

With such a tube fashioned in accordance with the invention, it is also possible for the inside of the tube to be provided with ribs or grooves. In the case in which grooves are provided cn'the inside surface of the tube, the said grooves are formed so as to be opposite to the ribs formed on the outside.

The production of tubes in accordance with the present invention is effected with rolls in which recesses or grooves are provided, preferably in the crest (middle or top) and in the trough plane (side) thereof, such recesses or grooves corresponding as regards their shape to the required ribs. The crests are at the middle region or top of the rolls and the trough on the sides of the tube.

The manufacture of tubes in accordance with the present invention can be effected in various ways, for example, it is possible to roll out a billet over a profiled mandrel with rolls of the type described above in order to obtain both an external and an internal profiling of the tube. However, it is also possible to roll out the billet with rolls of the type described over a smooth cylindrical mandrel and so to choose the rolling conditions that, for example, a smooth cylindrical inside surface is formed. Moreover, in order to produce tubes with two opposed external ribs, the recesses can be arranged only in the trough plane of the rolls, and, by

suitable dimensioning of the thickness of the tube wall before and after the rolling, it is possible to produce tubes in which the external ribs have grooves associated therewith on the inside surface of the tube without the necessity of employing a profiled mandrel.

The present invention may be more readily understood from the drawing which illustrates a cross-section of a tube manufactured in accordance with the present invention and in which a tube 1 is formed with external ribs 2 and internal grooves 3, which are formed in the inside surface of the tube 1 opposite to the external ribs 2.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

A cold pilger rolled seamless tube having external longitudinal ribs thereon and grooves inside the tube opposite the ribs formed by stepby-step cold pilger rolling, the ribs having high consolidation of material, high strength and improved surface.

References Cited in the file of this patent UNITED STATES PATENTS 185,375 Whitehouse Dec. 12, 1876 385,109 Garver et al. June 26, 1888 1,842,280 Neuberth Jan. 19, 1932 FOREIGN PATENTS 4,554 Great Britain Feb. 22, 1902 6,415 Great Britain Mar. 15, 1902 20,447 Great Britain Sept. 16, 1896 463,382 Great Britain Mar. 30, 1932 

